The physical design features of a circuit pack assembly have become important considerations as communications systems evolve to provide more capability using equipment that occupies less space. A common design approach for circuit pack assemblies is to package circuit functions into sub-assemblies or modules, especially in circuit pack assemblies including electronic and optical circuitry. In an effort to provide more functionality in a circuit pack assembly, the size of the modules is being reduced. With the closely packed components within a module, thermal effects as well as electromagnetic radiation therefore become significant concerns. For example, heat generated by components within the modules can become a problem because certain components have maximum operating temperatures. When these temperatures are exceeded, component and ultimately system performance suffers.
Unfortunately, solutions to each of these problems can often be at cross-purposes. For example, one approach for shielding other modules from electromagnetic radiation generated by components is to enclose each module with electrically conductive material to restrict electromagnetic radiation, e.g., to substantially seal the module. However, this solution actually leads to an increased build-up of heat within the module.
Various heat dissipation techniques are also known. One such approach is described in U.S. Pat. No. 5,757,621 wherein a heat sink is attached to a printed circuit board using standoff and spring combinations so that the heat sink makes the appropriate level of thermal contact with the electronic devices on the printed circuit board. Heat sinks having a plurality of vertically and upwardly extending fins which attach to circuit components are also known. Both of these types of heat dissipation arrangements require space on the circuit board assembly for mounting the heat sink as well as additional height clearance above the components. As such, these heat dissipation arrangements are not particularly well-suited in circuit pack assemblies which have substantial space limitations.